<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Bootstrap Template</title>
<meta name="viewport" content="width=device-width,initial-scale=1,user-scalable=no" />
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<link rel="stylesheet" type="text/css" href="../bootstrap3/css/bootstrap.css">
<link rel="stylesheet" type="text/css" href="../bootstrap3/font-awesome-4.7.0/css/font-awesome.css"/>
<style type="text/css">
div{
border: 1px solid red;
}
</style>
</head>
<body>
  <div class="row">
  <div class="col-md-3 col-sm-6">占3列</div>
  <div class="col-md-3 col-sm-6">占3列</div>
  <div class="col-md-3 col-sm-6" >占3列</div>
  <div class="col-md-3 col-sm-6">占3列</div>
  </div>
  <!-- 桌面尺寸一行3   pad一行2 手机一行1 -->
   <div class="row">
  <div class="col-md-4 col-sm-6 col-xs-12">占4列</div>
  <div class="col-md-4 col-sm-6 col-xs-12">占4列</div>
  <div class="col-md-4 col-sm-6 col-xs-12" >占4列</div>
  </div>
</body>
<script type="text/javascript" src="../bootstrap3/jquery.min.js"></script>
<script type="text/javascript" src="../bootstrap3/js/bootstrap.js"></script>
<script type="text/javascript" src="../bootstrap3/js/holder.js"></script>
<script type="text/javascript" src="../bootstrap3/js/html5shiv.min.js"></script>
<script type="text/javascript" src="../bootstrap3/js/css3-mediaqueries.js"></script>
<script type="text/javascript" src="../bootstrap3/js/respond.min.js"></script>
</html>